During the machining of bores in work pieces or other surfaces of different kinds, to obtain good results the bore should be measured for continuously establishing parameters such as bore diameter, taper and roundness. In the past this has been mainly accomplished with different types of gauges. This requires that the measurement must be made between grinding operations which of course increases the total process time to at least some extent. In mass-production, this is quite unacceptable.
To improve the process, and permit the measurement of bore diameter and taper, measurement fingers have been used which enter in the bore when the grinding wheel is removed. However, even in this case the measurement is made between the grinding operations which thus means relatively long grinding cycles. Also, the measurement fingers are not useful for roundness measurement and their use necessitates extra equipment for the machine, which is susceptible to damage when the measurement fingers are moved to and from measuring position. Furthermore this known kind of measuring mechanism has a relatively low resolution.
DE-A1-100 29 965 refers to a method and a device for contact-free load measurement of a rotating spindle for the purpose of tool supervision. The device incorporates at least one displacement sensor which measures position changes of the rotatable spindle in relation to the housing, caused by axial forces, radial forces or torques acting on a tool supported by the spindle. The resulting measurement signal curve for one revolution of the spindle without a load applied to the tool is thus representative for irregularities and out-off-roundness of the measured surface of the rotating spindle. The measurement signal curve is stored in an evaluation unit then is subtracted from the measurement signal curve for one revolution of the spindle with tool and spindle load in order to compensate for the part of the measurement signal curve caused by irregularities and out-off-roundness of the spindle itself. The evaluation unit emits an output representative only of the spindle and tool load. By repeated tests and with the aid of a rotational angle sensor, it is possible to obtain from the evaluation unit a curve representing the pure tool load without influence from spindle irregularities or out-off-roundness and without spindle load.